Creating Lesson Plans in Advance

I have completed lesson plans for Monday and Tuesday next week but now I'm trying to finish plans for Wednesday but I seem to be stuck. I feel like I don't want to create lesson plans that I might want to change contingent on the outcome of Tuesday's lesson. Another reason I am concerned about the success of my lesson plan on Wednesday is that I have my observation that day and it is going to be in one of the most difficult classes (management-wise). I want the opportunity for feedback concerning my classroom management skills and I guess that was not evident in my last observation because the class was overall well behaved. Now I want to make a lesson plan for Wednesday using individual whiteboards to promote collaboration and give me the ability to quickly get a formative assessment of the students ability but that was contingent on how well the students worked with the whiteboards on Tuesday. So now, I am trying to think of a back up plan for a lesson that does not require much time content-wise....